Title: New Study of Reaction Cross Sections and the Nucleon Density Distribution

Abstract

Reaction cross sections ({sigma}R) for 12C beam on 9Be, 12C, and 27Al targets and for 11Be beam on 9Be target were precisely measured systematically in the intermediate energy range. It is indicated that these all {sigma}R data were successfully reproduced by a modified Glauber calculation, which is expected to be applied for the determination of density distributions of other exotic nuclei.

Characteristic 4.44-MeV ..gamma.. rays from the first excited state of carbon were observed in coincidence with scattered 4.5-GeV/c ..pi../sup -/ mesons in counters and wire spark chambers. The ..gamma..-ray angular distribution in the momentum-transfer frame confirms the electric quadrupole nature of the transition and reveals the polarization of the recoiling /sup 12/C* nucleus so that density matrix elements can be determined. A simple model with no adjustable parameters, which employs the distorted-wave impulse approximation and uses electron scattering data to obtain the nuclear transition matrix elements, predicts the angular distribution of the pions and the polarization of the /sup 12/C*more » recoils very well. However, the absolute values of the measured cross sections are only half as large as the predicted ones. (AIP)« less

Scattering and reaction cross sections in the seven-nucleon system are calculated in a multiconfiguration resonating-group study which consists of t+/sup 4/He, n+/sup 6/Li, and n+/sup 6/Li/sup */ cluster configurations. The results show that the diffraction and interference features of the experimental angular distributions can be well explained, but that the calculated magnitudes of the differential cross sections are generally too large. In addition, it is found that the calculated total reaction cross sections for the t+/sup 4/He and n+/sup 6/Li channels are only 30--40 % of the measured values, indicating that, for a satisfactory explanation of all the important featuresmore » of the seven-nucleon system, more cluster configurations must still be incorporated into the resonating-group formulation.« less

We have measured ..cap alpha..+/sup 12/C total reaction cross sections (sigma/sub R/) at E/sub lab/ = 94 and 173 MeV/N using the attenuation method. Our data indicate a decreasing sigma/sub R/(E) at intermediate incident energies. These results, along with existing measurements, are in quantitative agreement with theoretical predictions for sigma/sub R/(E) which are based on nucleon-nucleon total cross sections.